A turntable of radius R=1.60 m and mass M=32.2 kg rotates counterclockwise in a horizontal plane with an initial angular speed of 4x rad/s. The fixed turntable bearing is frictionless. The turn table is in the shape of a uniform disc with the moment of inertia of this turntable being I = 0.5*MR2. kgm2/s? kgm/s? (a) What is the magnitude of angular momentum of this turntable? Answer: (b) What is the (magnitude of) the momentum of this turntable? Answer: Now a lump of clay of mass m=2.38 kg and negligible size is dropped onto the turntable from a small distance above it and immediately sticks to a point 1.50 m from the axis (c) Find the final angular speed of the clay and turntable. Answer: (d) What is the change of kinetic energy after the clay is dropped (i.e. KE_turntabl_and_clay - KE_turntable_alone)? Answer: (e) What is the (magnitude of) the momentum of the clay and turntable system? Answer: rad/s J? kgm/s?
Angular Momentum
The momentum of an object is given by multiplying its mass and velocity. Momentum is a property of any object that moves with mass. The only difference between angular momentum and linear momentum is that angular momentum deals with moving or spinning objects. A moving particle's linear momentum can be thought of as a measure of its linear motion. The force is proportional to the rate of change of linear momentum. Angular momentum is always directly proportional to mass. In rotational motion, the concept of angular momentum is often used. Since it is a conserved quantity—the total angular momentum of a closed system remains constant—it is a significant quantity in physics. To understand the concept of angular momentum first we need to understand a rigid body and its movement, a position vector that is used to specify the position of particles in space. A rigid body possesses motion it may be linear or rotational. Rotational motion plays important role in angular momentum.
Moment of a Force
The idea of moments is an important concept in physics. It arises from the fact that distance often plays an important part in the interaction of, or in determining the impact of forces on bodies. Moments are often described by their order [first, second, or higher order] based on the power to which the distance has to be raised to understand the phenomenon. Of particular note are the second-order moment of mass (Moment of Inertia) and moments of force.
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